Trusted users can report content as spam via a new link in the entity menu. When an entity gets enough reports it gets disabled. Administrators can see what was disabled due to spam, and who reported it. They can then unmark it as spam, or delete it, or just leave it disabled (if you want to collect spam data or something I guess). Additionally when the content gets disabled the owners of the reported content will get a strike against them, if they get too many strikes in too short of a time period they will get auto-banned.